| 摘要 |
A digital speaker unit is provided to generate a sound wave which is an original sound having a uniform frequency characteristic without distortion. A digital speaker unit includes a serial-parallel conversion unit(20), a plurality of ultrasound generators, and a low band pass sound filter(50). The serial-parallel conversion unit(20) converts a serial digital signal outputted from a sound processing apparatus(10) into a parallel digital signal. The plurality of ultrasound generators convert the parallel digital signal of n bits obtained from the serial-parallel conversion unit(20) into ultrasound waves of a corresponding size to each bit value classified by each bit. The ultrasound waves generated from the ultrasound generators(31-3n) are mixed into ultrasound waves of corresponding amplitude in a point of time at which the ultrasonic wave is sampled in a medium. An instrumental low band pass sound filter(50) reproduces a sound wave of an audible frequency band of the mixed ultrasound wave. The ultrasonic generator(31-3n) of each bit generates ultrasonic sounds of unit amplitude.
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